A TDR system measures the reflections of an incident waveform from impedance discontinuities in the system under test. Typical TDR systems could be sonar to detect underwater objects, ultrasound to detect objects inside the body and as described in this invention, voltage steps to detect discontinuities in electrical systems. A TDR pulse in a TDR system is typically a fast rising voltage step that repeats at a regular rate so an internal timebase can sample the reflections from the discontinuities.
TDR systems typically use a sequential sampling timebase to sample the TDR voltage step. A sequential sampling timebase samples the TDR waveform by delaying a sampling strobe from the trigger generated by the TDR voltage step. These delay circuits are inherently nonlinear and subject to large time jitter. The record length of a sequential sampling timebase is typically less than 10,000 samples independent of the sampling rate. As you increase the sampling rate, the record length stays the same so the time period of the record decreases.
Therefore it would be beneficial to provide an improved method and apparatus that overcomes the drawbacks of the prior art.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and the drawings.